That's A Moray Monday: The Baby Pictures Edition

Since last Monday was abuzz with Pharyngula-driven traffic on the whole Expelled brouhaha, I didn't get around to posting a Moray Monday. So I thought I'd make up for it with today's special edition focused on the early life stages of moray eels. Turns out morays aren't just cool as adults, they're pretty awesome as babies too.

True-eels (Anguilliformes) along with the closely allied tarpon (Megalopidae), bonefish (Albulidae), and ladyfish (Elopidae) produce larvae known as leptocephali. These transparent, ribbon-like larvae drift as part of the planktonic community as they develop. Interestingly, Muraenid (moray eel) leptocephali possess pectoral fins, a condition wholly different from that of the adults. It is during the transformation from leptocephalus to juvenile that the pectoral fins are resorbed.

Moray eels, like all true eels, are oviparous--or egg-laying. Although little is known regarding moray spawning, fecundity and early development of the leptocephali, one published source records numerous ripe eggs measuring 1mm in diameter from a 1.1 meter female. In contrast to this single record other sources indicate a much larger size for the eggs of other morays, on the order of 3-4mm in diameter. Interestingly, marine aquarists may have more direct experience with moray egg production than the research science community. I found posts on at least two online aquarist discussion boards about discovering egg masses in tanks housing Zebra morays. It's all anecdotal and no images were provided, but it's reasonable to assume this sort of thing does occur in captivity.

Leptocephalus of the Caribbean ocellated moray (Gymnothorax ocellatus)
(Fishes of the North Atlantic, 1989)
When the fertilized eggs of morays hatch, prolarvae emerge. Shortly thereafter the prolarvae transform into leptocephalus larvae, which grow to be between 5 and 10 cm in length. Leptocephali of the various species of moray in general are distinguishable by patterns of pigment, the number of trunk muscles (known as myomeres), and the position of the dorsal fin and the anus. The myomeres of a leptocephali can be clearly seen in the specimen in the image to the left (click image to enlarge).

The leptocephalus shares a number of morphological characteristics with its adult counterparts: both are long and laterally compressed and their dorsal, caudal and anal fins are continuous. Unlike adults, they have a "gelatinous" consistency and their tissues (with the exception of bone) are transparent. The leptocephalus larva will undergo its final metamorphosis in open water. Except with regard to size, the juvenile resembles the mature animal. Ocean currents disperse the animals after metamorphosis and, once they have reached a permanent habitat, they mature.

While not apparently practiced with moray larvae, the leptocephalii of the Japanese conger eel is eaten seasonally in the markets of Shizuoka, Okayama, Misaki, and Wakayama Prefectures. Known as “Noresore” (のれそれ), the baby conger eels are 5-6cm in length and resemble long transparent noodles (save for their eyes). At sushi counters, they are served with freshly grated ginger and chopped green onions. At some restaurants, they are served live to the table and eaten live after dipping in sweet fish sauce mixed with vinegar.

Who am I to critique? I eat hotdogs.